Global System for Mobile Communications (GSM) telecommunication systems provide wireless communication to mobile devices over a radio access network (RAN) operating in licensed bandwidth. A RAN typically consists of several macrocells, otherwise known as base transceiver stations (BTS). Each macrocell of a network is typically connected to a base station controller (BSC). The BSC controls and monitors various activities of the macrocells. For example, the BSC may help to coordinate handoff of a mobile device moving from one macrocell coverage area to another. The BSC may also coordinate operating bandwidth with neighboring macrocells to avoid interference. As the bandwidth used by mobile applications continues to increase, there is a demand to increase network capacity through frequency reuse.
Femtocells, picocells, and microcells, hereinafter referred to collectively as femtocells, are small, low-power base stations designed to provide better coverage for small residential structures, high-demand public locations or other hard to cover areas. Femtocells operate in a licensed spectrum with the authorization of the licensee and use a broadband data connection to send data to and receive data from the licensee network. Femtocells have a limited range of coverage, and as such, multiple femtocells may operate within a macrocell area.
Femtocells provide several advantages. For end-users, femtocells may reduce wireless data charges, improve indoor coverage, and reduce power consumption of mobile devices. For network operators, femtocells improve coverage, improve capacity by reducing the amount of macrocell bandwidth used, reduce traffic between a provider's macrocell and wired networks, and reduce the operator's maintenance and infrastructure costs.
Femtocells typically operate in one of two configurations. The femtocell may act as an extension to the existing network of macrocells network and provide coverage for all network users or the femtocell access may be limited to a particular set of users.
The placement and bandwidth spectrum utilized by a femtocell may adversely interfere with the operation of macrocells or other neighboring femtocells. In 3GPP Long Term Evolution (LTE) systems, connections are established in unique orthogonal frequency domain multiplexed (OFDM) subcarrier channels. LTE macrocells generally use the same frequency bands. Macrocells coordinate with each other to give mobile users at the edge of a macrocell coverage area a different subset of the available OFDM subcarriers to avoid interference. Like macrocells, femtocells must operate in using a set of OFDM subcarriers that are unique from its neighboring femtocells in order to avoid interference. Because femtocells operate outside of a coordinated network, similar coordination is generally not possible. One or more embodiments of the present invention may address one or more of these issues.